"Recent reports indicate these calls are using the '222' country code from the West African nation of Mauritania," the FCC said in a news release. "News reports have indicated widespread overnight calling in New York State and Arizona."

It works like this: the caller (most likely an automated robocaller) dials your number and hangs up almost immediately — typically after one ring, hence the scam's name. The same call may repeat several times in a row, especially in the overnight hours. Apparently, the scammer is betting you'll be concerned after waking up to repeated calls from the same number, and you'll call back to find out what's going on.

That's when the trap is sprung; calling back works like a 1-900 number, running up a huge toll charge you'll see on your next phone bill.

Since there's no way to cast this One Ring into the fires of Mount Doom, the FCC advises you never call back a phone number you don't recognize. You can also check with your wireless phone provider to block outgoing calls to international numbers. And, unless you know someone in Mauritania— you shouldn't be calling anyone with a (222) phone number.